Gears for two sets of wheels

[JohnF53]

Hi, I have a mountain bike which I use for fairy mild off-road riding, country parks and so on. I am thinking of getting another set of wheels so I can put some less knobbly tyres on them for some road use. (I've seen it said that you can just switch tyres on the same set of wheels, but that seems like too much faffing about to me).
So, my question is... if I get another set of wheels should the gearing be the same as the first set, at least in terms of numbers of sprockets on the cassette? I'm thinking that if the gear changer is set up for 9 sprockets and I then put an 8-sprocket wheel/cassette on it won't change properly.

What do you think?

 

[Cubist]

Yes, if you go down that route, the cassettes need to be the same number of cogs and the same size (ie range), otherwise the rear mech won't work properly. You might also like to think about having a different chain for each cassette to ensure they wear at the same rate. Alternatively, get used to swapping the cassette over at the same time as the wheels.

 

[ColinJ]

If you have rim brakes, make sure that both pairs of wheels have similar rims otherwise you will have to adjust your brakes every time you swap the wheels!

(I learned this the hard way, when I bought spare wheels for my first MTB ...)

 

[GilesM]

If your current chain and cassette is well used, and quite well worn, I'd suggest buying a new cassette for your existing wheels as well as your new ones, and also a new chain, if you swap them quite regularly you will find that they will both work fine with the same chain, they will all wear together, I would also suggest a closer ratio cassette for your new wheels with the road tyres, a 9 speed mtb one will probably be 11 to 32, for the road wheels 12 to 28 or 12 to 26 could be more useful.
As ColinJ mentions, check out the type of rims if you have rim brakes, and if you have disc brakes, a second set of rotors would be helpful, and if you have disc brakes I would recommend using the same hubs as you existing wheels, this will ensure the disc position perfectly matches the calliper position, right pain if you spend all of the cash on new wheels, tyres and cassette, but have to adjust the calliper position every time you change wheels.

 

[Psycolist]

If your bike is set up for a rear cassette with either 6,7 or 8 cogs, then, in theory, you could have 6,7 or 8 cogs on a different set, they would not need to have the same number of cogs as the mech movement spacing is the same on all 3. BUT, if you have 7 now, and fit an 8, only 7 would be accessable without major mech adjustment, or if you have a seven and fit a six, the chain will end up being taken off the cog altogether at one end or the other, again, without major mech adjustment, and by the time you have messed about re-indexing your gears at each changeover, you may as well keep to 1 set of wheels and change the tyres each time. If you are running a nine or ten speed cassette, both wheel sets would need to be the same.This sort of system of having two wheel sets, only really works well when you have two sets of matching wheels, with the same number of cogs on each set. The set with slick tyres, would, IMHO, need as mentioned by a previous reply, need to be a closer ratio. My own experience of this situation is that even with matching wheel sets, there is always a small mech adjustment needed to ensure proper indexing. The points made about chains and cassettes needing to be kept together are also well made. I used this method for dry weather, versus wet weather tyres on my road bike and find it works well enough, but can still be a bit of a nuisance at times. I now use a single wheel set with allweather tyres. As you dont sound like you do any serious off roading, I would be inclined to invest in a good pair of multi surface tyres that offer low rolling resistance on road but have good grip for the tow paths, parks and cycle paths.